1. Field of the Invention
The present invention relates to a content managing technique for improving convenience when transmitting and receiving via a network audio video (AV) content compressed and encoded from or to so called digital consumer electronic appliance products for household use, such as a digital versatile disk (DVD) recorder, a hard disk drive (HDD) video recorder, a personal computer, a personal digital assistant (PDA), or a cellular phone, for example.
2. Description of the Related Art
In recent years, networking of so called digital consumer electronic appliance products, such as DVD recorders or HDD video recorders, has progressed remarkably. For example, as is apparent from the efforts of the Digital Living Network Alliance (DLNA), great attention has been focused on connecting a plurality of digital consumer electronic appliance products via a network and exchanging AV content between them.
When content is transferred, two large problems exist in view of intra-equipment compatibility: (1) compatibility of protocols for use in transfer; and (2) a compression format of content to be transferred.
The DLNA has established a guideline in order to solve these problems. With respect to a compression format of item (2), compatibility is guaranteed by using a method for “specifying an essential format”. The problem which occurs here is that, in general, between a stationary household device and a mobile device for portable use, different compression formats are often used in view of processor capacity, memory consumption, power consumption or the like. For example, in terms of video content, a stationary device can conform to MPEG-2, and a mobile device can conform to MPEG-4.
In such a situation, for example, when an attempt is made to download and view video content which exists in a (stationary) household device by using a mobile device, it is necessary to convert MPEG-2 content to MPEG-4 content, and then, transfer the converted content. In the case where a household device includes a transcoder which converts MPEG-2 to MPEG-4, it is possible to achieve conversion using only the two devices of the parties concerned.
On the other hand, where the household device fails to include a transcoding function from MPEG-2 to MPEG-4, a third relay device can be used over a network to perform transcoding. This is a particularly effective technique in a closed world, such as a household network, where sharing the transcoding function or resources can be readily achieved.
However, where content is directly exchanged between the parties and where content is exchanged while a relay device is-interposed, there still remains a general problem that a predetermined amount of processing time is required for this transcoding.
In addition, as one technique for enhancing responsiveness, a method has been proposed for storing content converted by the transcoder in a cache after being converted (refer to Jap. Pat. Appln. KOKAI Publication No. 2004-526227, for example). According to this technique, for example, with respect to second and subsequent requests, it becomes possible to enhance system responsiveness.
The system described in the Jap. Pat. Appln. KOKAI Publication No. 2004-526227 is tailored for an unspecified number of users. For example, a so called majority rule is established for satisfying many more users from among all the users, for example, for determining the content stored in a cache after being converted using a Least Recently Used algorithm.
However, in digital consumer electronic appliance products for household use, it is necessary to properly respond to a specialized demand of each user.